Amphiprotic: definition in chemistry
Amphiprotic: Able both to donate and to accept a hydrogen ion (H⁺, a proton). Water and the hydrogen carbonate ion (HCO₃⁻) are common examples.
An amphiprotic species must have a hydrogen atom it can give away and a lone pair of electrons that can take one in. Every amphiprotic substance is also amphoteric, but not the other way around: aluminum oxide reacts with both acids and bases yet has no hydrogen to donate. Because water is amphiprotic, it can react with itself, forming small amounts of H₃O⁺ and OH⁻ ions.
Examples
- Water accepts H⁺ from HCl and donates H⁺ to ammonia
- HCO₃⁻ + H⁺ → H₂CO₃, and HCO₃⁻ + OH⁻ → CO₃²⁻ + H₂O
- Dihydrogen phosphate (H₂PO₄⁻) can gain or lose a hydrogen ion
- Amino acids such as glycine carry both an acidic and a basic group